Poison ivy and poison oak are two of the major causes of allergic contact dermatitis in the United States today. According to Dr. William Epstein, as reported in the Smithsonian, Volume 16, Number 5, dated August, 1985 by Noel Vietmeyer:                “Poison ivy and oak are by far the major causes of allergic contact dermatitis in the United States. More people suffer from them than from all other allergic skin diseases combined . . . No one counts the number of cases, but there are probably at least ten million a year, nationwide. Poison oak and poison ivy are possibly the greatest cause to workmen's disability in the nation: each year may bring more than 140,000 cases in the workplace, causing perhaps more than 152,000 lost work days.”        
According to Kligman (AMA Arhives of Dermatology, Vol. 77, February 1958, p. 149, et seq.,) the first significant advance in Rhus biochemistry was made by Majima (Ber. Deutsch Chem. Ges. 40:4390, 1907 and 50:172, 1922), working with urushiol. Urushiol is a yellow oil extracted from the Japanese lac tree. Later, McNair (J. Am. Chem. Soc. 43:159, 1921), studied poison oak and concluded that the active principle (lobinol) was a catechol with an unsaturated side chain, whose position and structure were not identified. Hill and his collaborators (J. Am. Chem. Soc. 56:2736, 1934) later hydrogenated poison ivy urushiol. They obtained a product identical with Majima's hydrourushiol from Japanese lac. They therefore wrongly concluded that the antigenic compounds in the American and Japanese plants were identical.
According to Kligman, however:                “The sole chemical difference between Japanese lac and poison ivy is the position of one of the unsaturated bonds of the triolefin.”        
Strangely, however, the allergen urushiol does not appear to affect animals and household pets. Cats and dogs can be exposed and actually play in the area without being affected, but can infect their owners by brushing up against their skin and transferring the urushiol on their coats to the unexposed areas of the human anatomy. According to Dr. Epstein, Ibid.:                “Between 15 and 25% of us are essentially immune, 25% are mildly sensitive and don't normally develop severe reactions, 25 to 30% are moderately sensitive and break out significantly with the amount of urushiol found in one leaf and 10 to 20% are so exquisitely sensitive that less than one leaf products intense dermatitis . . . . ”        
The oily substance urushiol, when in contact with the skin, penetrates the outer skin layers and begins to chemically bind to the skin cells. The body sees the combination of the urushiol in chemical combination with a skin cell as a foreign intruder. The immune system immediately rushes large white cells called macrophages and T-lymphocytes to destroy the affected skin cells. Dr. Epstein explains, Ibid:                “It's the body's own over-reaction that causes the complications. In sensitized persons, the area fills up with the white blood cells and they release so much cell-destroying toxins that they tear apart even the skin itself. That's what produces the blisters and suppurating sores.”        
Many folk remedies have been proposed for use after contact with urushiol. These include morphine (topically), bromine, kerosene, gun powder, iodine, aqua regia, buttermilk, cream and marshmallows. Additionally, innumerable botanicals, such as snake root, coffee, gelisium, hellebore, ipecac, lobelia, mustard, opium, stryhnine, veratrum, etc. have been suggested.
A major problem associated with skin contact with urushiol from poison oak, poison sumac and poison ivy is encountered by the foresters of the U.S. Forestry Service. This is particularly severe in the case of forest fires, where the soot and gases from the burning flames contain urushiol, which can get onto the foresters fighting the fire and even into their respiratory system. This is further complicated by the fact that the urushiol coats formites, such as clothing, utensils, even carbon and soot in the area of forest fires and can therefore provide another method of contact, even outside the area of the plants themselves.
Dr. Edward E. Waali, working under contract with the U.S. Forestry Service, tested many materials in an effort to find a chemical which would absorb or somehow chemically bind urushiol. Waali tested solid absorbents, such as silica gel, alumina and activated charcoal. Additionally, he saturated samples of cloth and mordanted them with salts of aluminum, copper and chromium.
Dr. William L. Epstein, also working under contract with the U.S. Forestry Service, became aware of Dr. Waali's work and tested a wide variety of agents, including Sure® antiperspirant and Drysol™, both of which contain the antiperspirant aluminum chlorohydrate. The Sure® antiperspirant, in the spray form, contains aluminum chlorohydrate, cyclomethicone, quaternium-18 hectorite, perfume, ethanol, isobutane and propane. This composition is reported from 1 to 5% quaternium-18 hectorite, an onium (equaternary ammonium) ion-exchanged hectorite clay. See for example, Clinical Toxicology of Commercial Products, Gosselin, et al., 5th edition, William and Watkins, 1984, PV-633.
Quaternium-18 hectorite is a reaction product of hectorite and quaternium-18 and is commercially available as Bentone 38 (NL Chemicals). Quaternium-18 (CAS Number 61789-80-8) is predominantly (90 to 100%) a quaternary salt that conforms generally to the formula:
wherein R1 and R2 represent hydrogenated tallow fatty radicals, R3 and R4 are methyl groups, and M− is a halide, acetate or hydroxide anion. It is well known that onium ions, e.g., quaternary ammonium ions, react with layered clay materials, such as hectorite, by ion-exchange of the positively charged nitrogen atom exchanging with exchangeable cations on the inner surfaces of the clay platelets. Such onium ion-exchanged clays, while being somewhat effective to sorb urushiol, have a relatively low capacity for urushiol sorption in comparison to the layered materials of the present invention.
Quaternium-18, quaternium-18 hectorite and quaternium-18 bentonite are organophilic clays that are generally considered safe as cosmetic ingredients and have been widely used as suspending agents for antiperspirants. See “Final Report on the Safety Assessment of Quaternium-18, Quaternium-18 Hectorite and Quaternium-18 Bentonite,” Journal of the American College of Toxicology, Vol. 1(2), 1982, pp. 71–83.
Accordingly, a need has continued to exist for an effective and cosmetically acceptable material to protect humans from the effects of skin contact with poison ivy and similar poisonous plants.
In 1989 Powell et al. patented an aerosol composition of organophilic clay dispersed in a cosmetically acceptable solvent (U.S. Pat. No. 4,861,584). This composition suffers from several drawbacks that include high cost, drying of the skin, allergic reaction in some individuals to quaternary ammonium compounds, relatively low sorption capacity for urushiol, incompatibility with most common cosmetically acceptable solvents, weak bonding of urushiol to the organophilic clay, and the need for polar activators, such as low molecular weight alcohols or ketones.